(1) Field of the Invention
The present invention relates generally to a device for measuring tension on a cable, and more particularly to a cantilevered load monitor sheave having height, angle and tilt adjustments.
(2) Description of the Prior Art
The measurement of tensile load within a cable as it is pulled around a sheave is a common component of cable testing. Various load measuring devices are well known in the art. U.S. Pat. No. 5,365,797 to McCrory, III, employs a split pulley with one end of the split being hinged and the other end allowed to open or close. A rope or cable is wrapped about the pulley and tension applied to the rope or cable causes the open end of the split pulley to begin to close. The amount of closure is measured using a strain gauge load cell and is proportional to the tensile load applied to the rope or cable. Many prior art devices operate on this general principle of measuring strain occurring in a member as a result of a load applied to the member. U.S. Pat. No. 3,248,937 to Vincent provides a revolving drum on a frame. A pawl mounted on the frame engages the drum. Tension on a line wrapped around the drum tries to rotate the drum against the pawl. A strain sensitive means is attached to the pawl and measures the dimensional change or compression of the pawl resulting from the load applied against the pawl by the drum. The amount of compression is proportional to the tension on the line.
The testing of sonar array cables presents a unique set of challenges in testing tension in the cable as it is pulled about a sheave. Due to the large bend radius of the cables, the sheave must have a minimum radius of 18 inches. Fabrication of a sonar array cable is accomplished with the full length of the cable laid out and testing is carried out on various sections of the cable. The sections of the cable are tested independently such that the cable is not put onto a reel until all sections have been tested. Therefor it is necessary to be able to test a section of the cable without threading the cable around the sheave. Rather, the apparatus must allow the cable to be looped over the sheave. As a result of fabrication methods and testing requirements, the height of the sheave and the tilt of the sheave axis must be adjustable. Further, the direction of the resultant tensile loading can vary from section to section, requiring the test apparatus to accommodate these angular changes. None of the prior art load monitoring sheaves provide the ability to loop the cable over the sheave combined with the necessary height, tilt and angular adjustments.